Cobalt removal

Brendlinger, D. L. and Tarsitano, J. J. Generalized Dermatitis due to Sensitivity to a Chrome-Cobalt Removable Partial Denture , Journal of the American Dental Association, 81, 392-394 (1970)... 

Some of the more prominent schemes for cobalt removal and recycle are ... 

This formula he afterwards modified to (2) in order to explain the fact that if two ammonia molecules fewer are present in the molecule, two acid residues become inactive and therefore must be directly linked to cobalt. Removing two ammonia molecules from scheme (2) yields the formula at that time given to the pcntanunino-salts, namely, in the ease of chloro-pentammino-cobaltic chloride,... 

Relatively few studies are available on cobalt removal from waters even though it is an important industrial material and may be toxic (though not as much as some of the other heavy metals). The dominant species in aqueous solutions is Co- [123]. The mononuclear hydrolysis products of Co(II) from CoOH to... 

Table 1 shows some representative results for cyclohexane oxidation with t-BHP over calcined Ti-UTD-l(Co) and Ti-UTD-1 (acid treated to remove cobalt [4]). In acetone the cyclohexane is converted to cyclohexanone as the major product with trace amounts of adipic acid as well as the other carboxylic acids and diketones in Scheme 1. Changing the solvent from acetone to t-butanol improves the conversion and the yield of adipic acid, however, the peroxide efficiency decreases. Increasing the amount of peroxide in the system also n proves conversion but the peroxide efficiency is decreased. The product distribution observed with the Ti-UTD-l(Co) sanqjles suggets a homolytic process catalyzed by cobalt. Removal of the cobalt lowers the activity in t-butanol but improves the peroxide efficiency. 

When the purification circuit at Trail Operations was upgraded in the early 1990s, a high-density, antimony-activated system was installed for cobalt removal (Figure 5). The expected advantages of this hot-stage purification system were ... 

Solid composition of the copper concentrate was analyzed over time ia each of the two campaigns. The results (Table XII) indicate that the copper concentrate was slightly emiched in copper content and depleted in iron, nickel and cobalt. The calculated values were 12.5 and 8.6% copper enrichment, 18.6 and 11.1% iron removal, 5.6 and 29.1% nickel removal and 1.8 and 20.0% cobalt removal for campaigns 1 and 2. More than 95% of the copper from the PLATSOL autoclave solutions was removed during the enrichment process, validating the process concept. 

After the copper and cobalt removal the PLS contains now almost purely NiS04(aq). The nickel can be recovered as cathodes from electrowinning or nickel powder from the hydrogen reduction In the electrowinning process, nickel is precipitated from a nickel sulphate solution into metallic form by electric current. The cathodic reaction is the reduction of nickel ions on the cathode and the anodic reaction is the oxidation of water on the surface of the lead anode. 

Kawamura, F., Funabashi, K., Kikuchi, M., Ohsumi, K. Using titanium oxide for cobalt removal from high-temperature water. Nucl. Technology 65, 332-339 (1984)... 

In water, NiO(OH) and Co(OH)2 yield Ni(OH)2 and the less soluble C02O3, thus making cobalt removable from some mixtures. 

Cobalt compounds have been in use for centuries, notably as pigments ( cobalt blue ) in glass and porcelain (a double silicate of cobalt and potassium) the metal itself has been produced on an industrial scale only during the twentieth century. Cobalt is relatively uncommon but widely distributed it occurs biologically in vitamin B12 (a complex of cobalt(III) in which the cobalt is bonded octahedrally to nitrogen atoms and the carbon atom of a CN group). In its ores, it is usually in combination with sulphur or arsenic, and other metals, notably copper and silver, are often present. Extraction is carried out by a process essentially similar to that used for iron, but is complicate because of the need to remove arsenic and other metals. 

Protein-Based Adhesives. Proteia-based adhesives are aormaHy used as stmctural adhesives they are all polyamino acids that are derived from blood, fish skin, caseia [9000-71 -9] soybeans, or animal hides, bones, and connective tissue (coUagen). Setting or cross-linking methods typically used are iasolubilization by means of hydrated lime and denaturation. Denaturation methods require energy which can come from heat, pressure, or radiation, as well as chemical denaturants such as carbon disulfide [75-15-0] or thiourea [62-56-6]. Complexiag salts such as those based upon cobalt, copper, or chromium have also been used. Formaldehyde and formaldehyde donors such as h exam ethyl en etetra am in e can be used to form cross-links. Removal of water from a proteia will also often denature the material. 

Thiophene [110-02-17, C H S, and dibenzothiophene [132-65-OJ C22HgS, are models for the organic sulfur compounds found in coal, as well as in petroleum and oil shale. Cobalt—molybdenum and nickel—molybdenum catalysts ate used to promote the removal of organic sulfur (see Coal CONVERSION... 

The conversion of CO to CO2 can be conducted in two different ways. In the first, gases leaving the gas scmbber are heated to 260°C and passed over a cobalt—molybdenum catalyst. These catalysts typically contain 3—4% cobalt(II) oxide [1307-96-6] CoO 13—15% molybdenum oxide [1313-27-5] MoO and 76—80% alumina, JSifDy and are offered as 3-mm extmsions, SV about 1000 h . On these catalysts any COS and CS2 are converted to H2S. Operating temperatures are 260—450°C. The gases leaving this shift converter are then scmbbed with a solvent as in the desulfurization step. After the first removal of the acid gases, a second shift step reduces the CO content in the gas to 0.25—0.4%, on a dry gas basis. The catalyst for this step is usually Cu—Zn, which may be protected by a layer of ZnO. 

AHoys can be produced by the coreduction process, carried out at 1000°C with calcium, from the oxide mixture. For example, samarium oxide [12060-58-1] and cobalt oxide are coreduced to a SmCo [12017-68-4] powder, CaO then being removed. 

Cementation is also an efficient way of putifyiag a pregnant solution by removing impurities that are more noble than the metal being processed. An example is the cementation of copper, cadmium, cobalt, and nickel from ziac solutions prior to electrowinning. 

Gas Reduction. The use of a gaseous reduciag agent is attractive because the metal is produced as a powder that can easily be separated from the solution. Carbon dioxide, sulfur dioxide, and hydrogen can be used to precipitate copper, nickel, and cobalt, but only hydrogen reduction is appHed on an iadustrial scale. In the Sherritt-Gordon process, the excess ammonia is removed duting the purification to achieve a 2 1 ratio of NH iNi ia solution. Nickel powder is then precipitated by... 

Other Meta.Is, Although most cobalt is refined by chemical methods, some is electrorefined. Lead and tin are fire refined, but a better removal of impurities is achieved by electrorefining. Very high purity lead is produced by an electrochemical process using a fluosiUcate electrolyte. A sulfate bath is used for purifying tin. Silver is produced mainly by electrorefining in a nitrate electrolyte, and gold is refined by chemical methods or by electrolysis in a chloride bath. 

Natural gas contains both organic and inorganic sulfur compounds that must be removed to protect both the reforming and downstream methanol synthesis catalysts. Hydrodesulfurization across a cobalt or nickel molybdenum—zinc oxide fixed-bed sequence is the basis for an effective purification system. For high levels of sulfur, bulk removal in a Hquid absorption—stripping system followed by fixed-bed residual clean-up is more practical (see Sulfur REMOVAL AND RECOVERY). Chlorides and mercury may also be found in natural gas, particularly from offshore reservoirs. These poisons can be removed by activated alumina or carbon beds. 

Eigure 3 is a flow diagram which gives an example of the commercial practice of the Dynamit Nobel process (73). -Xylene, air, and catalyst are fed continuously to the oxidation reactor where they are joined with recycle methyl -toluate. Typically, the catalyst is a cobalt salt, but cobalt and manganese are also used in combination. Titanium or other expensive metallurgy is not required because bromine and acetic acid are not used. The oxidation reactor is maintained at 140—180°C and 500—800 kPa (5—8 atm). The heat of reaction is removed by vaporization of water and excess -xylene these are condensed, water is separated, and -xylene is returned continuously (72,74). Cooling coils can also be used (70). 

Most of the heavy-metal impurities present in 2inc salt solutions must be removed before the precipitation reaction, or these form insoluble colored sulfides that reduce the whiteness of the 2inc sulfide pigment. This end is usually achieved by the addition of 2inc metal which reduces most heavy-metal ions to their metallic form. The brightness of 2inc sulfide can be improved by the addition of a small amount of cobalt salts (ca 0.04% on a Co/Zn basis) (20). Barium sulfate [7727-43-7] formed in the first step is isolated and can be used as an extender. 

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